Canon EF 135mm f2L USM - Manual (Page 5)

ENG-4
See your camera’s instructions for details on
mounting and detaching the lens.
¡After detaching the lens, place the lens with the
rear end up to prevent the lens surface and
electrical contacts from getting scratched.
¡If the contacts get soiled, scratched, or have
fingerprints on them, corrosion or faulty
connections can result. The camera and lens
may not operate properly.
¡If the contacts get soiled or have fingerprints on
them, clean them with a soft cloth.
¡If you remove the lens, cover it with the dust
cap. To attach it properly, align the lens mount
index and the
K index of the dust cap as shown
in the diagram, and turn clockwise. To remove it,
reverse the order.
1. Mounting and Detaching the Lens 2. Setting the Focus Mode
After autofocusing in ONE SHOT AF mode, focus
manually by pressing the shutter button halfway
and turning the focusing ring. (Full-time manual
focus)
To shoot in autofocus (AF) mode, set the focus
mode switch to AF.
To use only manual focusing (MF), set the focus
mode switch to MF, and focus by turning the
focusing ring. The focusing ring always works,
regardless of the focus mode.